I would have just guessed it was an aging flower (the one with "bleached" tips) but I take it all flowers opened at the same time?

I would think that the two flowers are slightly different ages. But I have had many open flowers so far (I counted 83), some already senesced, and none have exhibited any deviations from homogenously colored petals at any time. I have always assumed that the whole petal develops at a pretty equal rate, but perhaps that is not the case.

Update:Soon after that pic was taken yesterday, I watered the garden. Now, 25 hours later, both anomalies have almost disappeared!

And all the colchicums seem happier. If there was a water deficit for that one bulb, and petal development differs from one end of a petal to the other, I suppose that could explain it. As Trond says, next year's bloom should tell.

This one is related to C. lingulatum that grows on higher habitats (500-2300 m).Botanically speaking there are differences in leaf shape and in the number of flowers on a bulb (2-5 for C. lingulatum - 1-2 for C. sfikasianum).

A first flower for this season on one of the plants in the C. cupanii complex. These suffered a lot during last winter with a lot of dead one's as a result. Colchicum cupanii var. pulverulentum from Zaghouan Tunesia.